Advice on HVAC & Insulation issues

11 years ago

I have a few questions that I would love to have input on (from someone who doesn't have a vested interest!) I live in Atlanta, GA and have 2 HVAC systems on the main and second story that are original to my 1996 house. My electricity bills top out at around $500 in the summer with the thermostat set to 78 degrees.

1. Is it really cheaper to replace an HVAC unit in the winter or is that just a sales tactic to get me to replace it now? Ours isn't dead, just not running very efficiently. I'm thinking about letting it run until it dies and at that point replacing it with one of the contractors I have already found and gotten a quote from, but I'm also realistic about the fact that I don't have much time left on our current units.

2. Our ductwork is mostly laying on the floor of our attic and is not suspended. We are paying to have more insulation added (which I'm hoping will help the units run more efficiently). Can they spray fiberglass insulation directly over the ductwork?

3. I know there is some air leakage into our attic and I can see that some of the current fiberglass insulation is a bit dirty. How important is it really to have the attic floor air sealed?

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Comments (4)

energy_rater_la
11 years ago
some companies offer better prices when work is slow. some just have more time to do a better install.

duct work should be suspended, with 3" wide duct strap, duct
saddles etc. runs should be tight with smooth bends & no restrictions.
ducts lying on or buried in insulation in hot humid climates will
condensate. ducts that aren't straight & tight will reduce air flow
as will restrictions.

sealing the attic floor/ceiling of interior of house is the most
important leakage to address.
dirt on insulation is an indication of a leakage site below the
insulation. same goes for duct work insulation, dirt trails
on duct insulation lines up with leakage sites on duct collars
& ducts.
you can air seal the attic floor from inside the attic. pita...but
it can be done. then move inside & air seal at ceiling.
caulking moldings to ceiling & walls, taking supply vent
grills, bath fan covers etc off & using a mastic tape to seal
the over sized cut in the ceiling around these areas.
same with recessed lights, over sized cuts in ceiling hidden
by trim kits.

a bucket of mastic will go a long way to sealing duct take offs
at the plenum. mastic tape at plenum to equipment connections
etc

insulation slows air flow, it doesn't stop it. this is why you

see the dirt trails thru the insulation.

tell us more.

this is the method I use to seal supply boxes, bath fans
& recessed light over sized cuts in sheet rock. hardcast brand
1402 mastic tape is the only product I've found that makes
a good long lasting & strong seal.

I can walk you through a lot of the sealing work, I've

done hundreds of jobs!

pic of sealed supply box

best of luck
cinamn808 thanked energy_rater_la
cinamn808
Original Author
11 years ago
Great feedback, thank you so much!
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stickman42
11 years ago
Maybe a silly question, but what is all the black in the duct boot?
energy_rater_la
11 years ago
insulation. the supply boxes are insulated internally.